Many power tools, such as drills, drivers, and fastening tools, have a mechanical clutch that interrupts power transmission to the output spindle when the output torque exceeds a threshold value of a maximum torque. Such a clutch is a purely mechanical device that breaks a mechanical connection in the transmission to prevent torque from being transmitted from the motor to the fastening mechanism of the tool, such as a spindle or a pulling mechanism. The maximum torque or maximum pull force threshold value may be user adjustable, often by a clutch collar that is attached to the tool between the tool and the tool holder or chuck. The user may rotate the clutch collar among a plurality of different positions for different maximum torque settings. The components of mechanical clutches tend to wear over time, and add excessive bulk and weight to a tool.
Some power tools additionally or alternatively include an electronic clutch. Such a clutch electronically senses the output torque or output force (e.g., via a transducer) or infers the output torque or output force (e.g., by sensing another parameter such as current drawn by the motor). When the electronic clutch determines that the sensed output torque exceeds a threshold value, it interrupts or reduces power transmission to the output, either mechanically (e.g., by actuating a solenoid to break a mechanical connection in the transmission) or electrically (e.g., by interrupting or reducing current delivered to the motor, and/or by actively braking the motor). Existing electronic clutches tend to be overly complex and/or inaccurate and fail to include a method by which a user can verify if the installed fastener has been installed correctly.
This section provides background information related to the present disclosure which is not necessarily prior art.